Aluminum alloy



Patented Nov. 2 1937 ALUMINUM ALLOY John Bartow Bates, Euclid, Ohio, assignor to Titanite Alloys Corporation, Euclid, Ohio, a

corporation of Ohio No Drawing.

Application March 10, 1936,

Serial No. 68,086

2 Claims.

This invention relates to aluminum alloys and more particularly to alloys adapted for making castings that do not require subsequent heat treatment. The invention has for its main object the improvement of the aluminum-manganese-titanium alloy described and claimed in my prior application .Serial No. 751,588, filed November 5, 1934, by the addition of other metals thereto, for the purpose of modifying the charac- 1 teristics of the aluminum-manganese-titanium alloy so as to provide an alloy better adapted for certain types of castings.

A further object of my invention is to provide an improved aluminum-manganese-titanium base .5 alloy that will possess the properties ofhigh tensile strength and sufiicient elongation to meet the requirements for certain types of castings that have heretofore been made from other alloys that require subsequent heat treatment in no orderto give to the castings the desired physical qualities. This results in a material reduction in the cost of manufacture of such castings.

A further object of the invention is to provide an aluminum-manganese-titanium base alloy having copper added thereto for the purpose of increasing the tensile strength and at the same time provide an alloy which, when melted, has suflicient fluidity and melts at a s'ufiiciently low temperature to make satisfactory castings varying widely in cross-sectionand configuration.

As a result of my investigation of alloys of aluminum, manganese and titanium and made in accordance with my prior invention as described and claimed in my said application Serial No. 3:, 751,588, I have found that an alloy containing 1.75% manganese, 0.17% titanium and the balance aluminum, when cast in a graphite test-bar mold, shows tensile strength of 25,000 lbs. per square inch with 20% elongation. The same 40 alloy cast in a sand test-bar mold shows a tensile strength of 23,000 lbs. per square inch and a 10% elongation. I have discovered that by adding 0.5% magnesium to this alloy, a test-bar made in a graphite mold shows a tensile strength 45 of 28,000'to 29,000 lbs. per square inch with 14% elongation, and when cast in a sand-mold shows 27,000 1bs. tensile strengthwith 5% elongation.

These results develop after a normal aging period 1 of from two to three weeks.

I have also discovered that by reducing the manganese in the above aluminum-manganesemagnesium-titanium alloy to 1.50% and adding 1.50% of copper this alloy, when cast in a sand test-bar mold, can be made to develop a tensile strength of 30,000 lbs. per square inch with 4.5% elongation after aging.

The silicon in an alloy to be used in a sand I mold must be kept low and, as there is suflicient silicon in commercial 99% aluminum to combine 5 with the magnesium, in the aging process, no silicon is added in making the alloy. For a chill-cast alloy the silicon is necessary, up to about 2.5% to overcome the shrinkage characteristics and, while this relatively high percentage of silicon affects the elongation somewhat, the latter is not lowered to a point where the utility of the alloy is destroyed.

I have discovered that the addition of 2.0 to 2.5% of zinc to the above aluminum-manganesetitanium-magnesium alloy improves the casting quality of the alloy considerably without chang- .ing its tensile strength or elongation, and the zinc also increases the fluidity and allows a lower pouring temperature. Thus, while the effect of the added zinc is to improve its casting qualities, the physical characteristics of the alloy are not materially changed.

The vfollowing is an example of an alloy made in accordance with this invention:

9 Per cent Manganese r 1.25 Copper 1.25 Magnesium 0.25 to 0.50 Titanium 0.15 to 0.18

Balance-commercial aluminum with attendant impurities not in excess of 1%.

Balance-commercial aluminum.

To either of the above alloys pure zinc to the extent of 0.02 to 5.0% may be added with beneflcial results as to the casting qualities of the alloy, without affecting the tensile strength or elongation materially. I have also found that alloys made in accordance with my invention may contain up to 1.2% of iron without detrimental eflect. While I do not recommend adding iron to the alloy, some iron will be incidentally picked up from iron crucibles and ladies and I have 01' copper, 0.1 to 4.9% of magnesium, 0.1 to 4 9% 01' silicon," the aggregate amount of the magnesium and silicon iree and combined as magnesium siiicicle being limited to 5% of the alloy,

and the balance commercial aluminum having 5 impurities not in excess of 1.0%.

2. A casting alloy consisting of 0.5 to 5.0% of manganese, 0.05 to 0.5% of titanium, 0.5 to 8.0% of copper, 0.1 to 4.9% of magnesium, 0.1 to 4.9% of silicon, the aggregate amount 0! the magnesium and silicon free and combined as magnesium silicide being limited to 5% of the alloy, 0.02 to 5% 01' zinc, and the balance commercial aluminum having impurities not in ex-' cess of 1.0%.

JOHN BARTOW BATES. 

